In general, an integrated circuit refers to an electrical circuit contained on a single monolithic chip containing active and passive circuit elements. Integrated circuits are fabricated by diffusing and depositing successive layers of various materials in a preselected pattern on a substrate. The materials can include semiconductive materials such as silicon, conductive materials such as metals, and low dielectric materials such as silicon dioxide. Of particular significance, the semiconductive materials contained in integrated circuit chips are used to form almost all of the ordinary electronic circuit elements, such as resistors, capacitors, diodes, and transistors.
Integrated circuits are used in great quantities in electronic devices, such as digital computers, because of their small size, low power consumption, and high reliability. The complexity of integrated circuits range from simple logic gates and memory units to large arrays capable of complete video, audio and print data processing. Presently, however, there is a demand for integrated circuit chips to accomplish more tasks in a smaller space while having even lower operating voltage requirements.
As stated above, integrated circuit chips are manufactured by successively depositing layers of different materials on a substrate. Typically, the substrate is made from a thin slice or wafer of silicon. The active and passive components of the integrated circuit are then built on top of the substrate. The components of the integrated circuit can include layers of different conductive materials such as metals and semiconductive materials surrounded by low dielectric insulator materials. In attempting to improve integrated circuit chips, attention has been focused upon reducing the thickness of the layers while improving performance.
For instance, one area of circuit chip technology needing improvement is in the deposition of insulator or dielectric materials used in the chips. Such an insulator material should have a very high resistivity, as low as possible dielectric constant, and sustainability of subsequent process steps and materials used in chip manufacturing. The low dielectric insulator materials are incorporated into integrated circuits in order to reduce power dissipation when the circuit is in use.
Thin dielectric layers are being used routinely in the manufacturing of semiconductor devices for applications such as gates, capacitor dielectrics, besides various other uses. The most prevalent dielectric used in semiconductor devices is silicon dioxide, which can be formed through the reaction of oxygen and silicon at high temperature. Alternatively, steam can be reacted with silicon at high temperature to form silicon dioxide. In the past, silicon dioxide layers have been formed in conventional batch furnaces. Recently, as opposed to batch furnaces, such layers have also been formed in rapid thermal processing systems. The use of rapid thermal processing systems offers the advantages of short time high temperature processing which provides process advantages over using conventional furnaces.
In many advanced applications, silicon dioxide layers need to be doped with desired amounts of a dopant, such as a nitrogen specie, in order to improve the performance of the dielectric. The method by which the nitrogen dopant is incorporated into a silicon dioxide dielectric layer is complicated since it is necessary to control not only the concentration of nitrogen incorporated into the silicon dioxide but also its location within the oxide layer.
As described above, in order to produce advanced, fast acting devices, a need currently exists for producing dielectric layers having a minimal thickness. As the thickness of such dielectric layers decreases, however, significant difficulties arise in being able to properly and repeatably create thin nitrogen doped layers. In fact, even conventional 30 second to 120 second heating cycles conducted in rapid thermal processing chambers that are used to produce such layers become too long to provide controls sufficient to meet some of the requirements that are currently being specified.
Thus, a need currently exists for a process for producing thin dielectric layers that are uniform and that have improved electrical properties. A need also exists for a process for doping thin oxide layers. A need further exists for a rapid process for forming thin silicon dioxide layers doped with a nitrogen species.